Piezoelectric vibration piece and piezoelectric vibration device using same

Abstract

A piezoelectric vibration piece has an inverted mesa-type structure, comprising a thinned portion serving as a vibration region at a central part of a piezoelectric plate; and a thickened portion formed all along or partly along perimeter of the thinned portion to reinforce the thinned portion. In the piezoelectric vibration piece, contact metals including a large number of discrete metallic thin films are provided on the whole surfaces of the piezoelectric plate. A piezoelectric vibration device comprises the piezoelectric vibration piece which is housed in a package, wherein extraction electrodes of the piezoelectric vibration piece are connected to internal terminals of the package through a conductive adhesive. These structural and technical advantages prevent undesirable flowage of the conductive adhesive before thermal curing. As a result, the piezoelectric vibration piece and the piezoelectric vibration device comprising the same successfully attain excellent vibration characteristics.

The invention claimed is: 
     
       1. A piezoelectric vibration piece, comprising:
 a piezoelectric plate having a thinned portion serving as a vibration region at a central part thereof, and a thickened portion formed all along or partly along perimeter of the thinned portion to reinforce the thinned portion; 
 driving electrodes formed on upper and lower surfaces of the thinned portion of the piezoelectric plate; and 
 extraction electrodes for externally extracting the driving electrodes, wherein 
 the thickened portion has a first inclined side wall surface facing the thinned portion, and 
 a contact metal including a large number of discrete metallic thin films is formed on at least the first inclined side wall surface. 
 
     
     
       2. The piezoelectric vibration piece as claimed in  claim 1 , wherein
 the thickened portion is partly formed in an electrode-extracting region substantially equal in thickness to the thinned portion, 
 end parts of the extraction electrodes are extracted to the electrode-extracting region, 
 the thickened portion has, in a part thereof, at least two opposing second inclined side wall surfaces facing the electrode-extracting region, and 
 the contact metal is provided on not less than one of the at least two opposing second inclined side wall surfaces. 
 
     
     
       3. The piezoelectric vibration piece as claimed in  claim 2 , wherein
 the contact metal is provided on the at least two opposing second inclined side wall surfaces. 
 
     
     
       4. The piezoelectric vibration piece as claimed in  claim 2 , wherein
 the contact metal is further provided in the electrode-extracting region. 
 
     
     
       5. The piezoelectric vibration piece as claimed in  claim 1 , wherein
 the contact metal is made of a metal selected from Cr, Ru, Mo, and W, and 
 the contact metal has a thickness between 10 Å and 30 Å. 
 
     
     
       6. The piezoelectric vibration piece as claimed in  claim 5 , wherein
 the contact metal is provided on whole upper and lower surfaces of the piezoelectric plate, and the electrodes are provided on the contact metals. 
 
     
     
       7. The piezoelectric vibration piece as claimed in  claim 1 , wherein
 the thickened portion is provided on one of or both of the upper and lower surfaces of the thinned portion of the piezoelectric plate. 
 
     
     
       8. The piezoelectric vibration piece as claimed in  claim 1 , wherein
 the driving electrodes comprise a common electrode provided on one of the surfaces of the piezoelectric plate, and at least a pair of divided electrodes provided correspondingly to the common electrode on another one of the surfaces of the piezoelectric plate. 
 
     
     
       9. The piezoelectric vibration piece as claimed in  claim 1 , wherein
 the thinned portion is rectangular in planer view, serving as a vibration region, 
 the thickened portion is formed along perimeter of the thinned portion and having at least a pair of corner sections diagonally opposite to each other, 
 end parts of a pair of extraction electrodes for extracting the common electrode are formed at the at least a pair of corner sections of the thickened portion, and recesses are formed at the at least a pair of corner sections, 
 the contact metal is provided in the recesses, and end parts of the pair of extraction electrodes are respectively provided on the contact metals. 
 
     
     
       10. The piezoelectric vibration piece as claimed in  claim 1 , wherein
 an AT-cut crystal plate constitutes the piezoelectric plate. 
 
     
     
       11. A piezoelectric vibration device at least comprising the piezoelectric vibration piece as claimed in  claim 1 , and a package in the form of a shallow box with an open upper surface, the package having internal terminals formed in an inner bottom part thereof, and
 the piezoelectric vibration piece is housed in the package, and the extraction electrodes of the piezoelectric vibration piece are connected to the internal terminals through a conductive adhesive.